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Fan X, Ye Y, Saha A, Peng L, Pindi C, Wang Q, Yang L, Liu J, Tang X, Palermo G, Liao J, Xu T, Lu Y, Du G. Fine-tuning pH sensor H98 by remote essential residues in the hydrogen-bond network of mTASK-3. Int J Biol Macromol 2024; 273:132892. [PMID: 38878921 DOI: 10.1016/j.ijbiomac.2024.132892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 05/21/2024] [Accepted: 06/02/2024] [Indexed: 06/23/2024]
Abstract
TASK-3 generates a background K+ conductance which when inhibited by acidification depolarizes membrane potential and increases cell excitability. These channels sense pH by protonation of histidine residue H98, but recent evidence revealed that several other amino acid residues also contribute to TASK-3 pH sensitivity, suggesting that the pH sensitivity is determined by an intermolecular network. Here we use electrophysiology and molecular modeling to characterize the nature and requisite role(s) of multiple amino acids in pH sensing by TASK-3. Our results suggest that the pH sensor H98 and consequently pH sensitivity is influenced by remote amino acids that function as a hydrogen-bonding network to modulate ionic conductivity. Among the residues in the network, E30 and K79 are the most important for passing external signals near residue S31 to H98. The hydrogen-bond network plays a key role in selectivity or pH sensing in mTASK-3, and E30 and S31 in the network can modulate the conductive properties (E30) or reverse the pH sensitivity and selectivity of the channel (S31). Molecular dynamics simulations and pK1/2 calculation revealed that double mutants involving H98 + S31 primarily regulate the structure stability of the pore selectivity filter and pore loop regions, further strengthen the stability of the cradle suspension system, and alter the ionization state of E30 and K79, thereby preventing pore conformational change that normally occurs in response to varying extracellular pH. These results demonstrate that crucial residues in the hydrogen-bond network can remotely tune the pH sensing of mTASK-3 and may be a potential allosteric regulatory site for therapeutic molecule development.
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Affiliation(s)
- Xueming Fan
- Department of Pain Management, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China; Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China
| | - Yifei Ye
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China; Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China
| | - Aakash Saha
- Department of Bioengineering, University of California Riverside, 900 University Avenue, Riverside, CA 92521, United States
| | - Li Peng
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China
| | - Chinmai Pindi
- Department of Bioengineering, University of California Riverside, 900 University Avenue, Riverside, CA 92521, United States
| | - Qi Wang
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China; Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China
| | - Linghui Yang
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China
| | - Jin Liu
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China; Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China
| | - Xiangdong Tang
- Sleep Medicine Center, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China; Mental Health Center, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China; State Key Laboratory of Biotherapy, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China
| | - Giulia Palermo
- Department of Bioengineering, University of California Riverside, 900 University Avenue, Riverside, CA 92521, United States
| | - Jiayu Liao
- Department of Bioengineering, University of California Riverside, 900 University Avenue, Riverside, CA 92521, United States; Huaxi-Cal Research Center for Predictive Intervention Medicine, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China
| | - Tingting Xu
- Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guizhou, Guangdong 510530, China
| | - Yongzhi Lu
- Guangzhou National Laboratory, Guangzhou International Bio Island, Guangzhou, Guangdong 510005, China.
| | - Guizhi Du
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Centre of Translational Medicine of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610000, China; Department of Anesthesiology, West China Hospital of Sichuan University, Chengdu, Sichuan 610041, China.
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2
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Lin H, Li J, Zhang Q, Yang H, Chen S. C-type inactivation and proton modulation mechanisms of the TASK3 channel. Proc Natl Acad Sci U S A 2024; 121:e2320345121. [PMID: 38630723 PMCID: PMC11046659 DOI: 10.1073/pnas.2320345121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 03/19/2024] [Indexed: 04/19/2024] Open
Abstract
The TWIK-related acid-sensitive K+ channel 3 (TASK3) belongs to the two-pore domain (K2P) potassium channel family, which regulates cell excitability by mediating a constitutive "leak" potassium efflux in the nervous system. Extracellular acidification inhibits TASK3 channel, but the molecular mechanism by which channel inactivation is coupled to pH decrease remains unclear. Here, we report the cryo-electron microscopy structures of human TASK3 at neutral and acidic pH. Structural comparison revealed selectivity filter (SF) rearrangements upon acidification, characteristic of C-type inactivation, but with a unique structural basis. The extracellular mouth of the SF was prominently dilated and simultaneously blocked by a hydrophobic gate. His98 protonation shifted the conformational equilibrium between the conductive and C-type inactivated SF toward the latter by engaging a cation-π interaction with Trp78, consistent with molecular dynamics simulations and electrophysiological experiments. Our work illustrated how TASK3 is gated in response to extracellular pH change and implies how physiological stimuli might directly modulate the C-type gating of K2P channels.
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Affiliation(s)
- Huajian Lin
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai200125, China
| | - Junnan Li
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai200241, China
| | - Qiansen Zhang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai200241, China
| | - Huaiyu Yang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai200241, China
| | - Shanshuang Chen
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai200125, China
- Department of Otolaryngology-Head and Neck Surgery, Ninth People’s Hospital, Shanghai200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai200125, China
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Wang J, Liu H, Sun Z, Zou X, Zhang Z, Wei X, Pan L, Stalin A, Zhao W, Chen Y. The Inhibitory Effect of Magnolol on the Human TWIK1 Channel Is Related to G229 and T225 Sites. Molecules 2023; 28:6815. [PMID: 37836658 PMCID: PMC10574557 DOI: 10.3390/molecules28196815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 09/01/2023] [Accepted: 09/25/2023] [Indexed: 10/15/2023] Open
Abstract
TWIK1 (K2P1.1/KCNK1) belongs to the potassium channels of the two-pore domain. Its current is very small and difficult to measure. In this work, we used a 100 mM NH4+ extracellular solution to increase TWIK1 current in its stable cell line expressed in HEK293. Then, the inhibition of magnolol on TWIK1 was observed via a whole-cell patch clamp experiment, and it was found that magnolol had a significant inhibitory effect on TWIK1 (IC50 = 6.21 ± 0.13 μM). By molecular docking and alanine scanning mutagenesis, the IC50 of TWIK1 mutants G229A, T225A, I140A, L223A, and S224A was 20.77 ± 3.20, 21.81 ± 7.93, 10.22 ± 1.07, 9.55 ± 1.62, and 7.43 ± 3.20 μM, respectively. Thus, we conclude that the inhibition of the TWIK1 channel by magnolol is related to G229 and T225 on the P2- pore helix.
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Affiliation(s)
- Jintao Wang
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China; (J.W.); (H.L.); (Z.S.); (X.Z.); (Z.Z.); (X.W.); (W.Z.)
| | - Huan Liu
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China; (J.W.); (H.L.); (Z.S.); (X.Z.); (Z.Z.); (X.W.); (W.Z.)
| | - Zhuolin Sun
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China; (J.W.); (H.L.); (Z.S.); (X.Z.); (Z.Z.); (X.W.); (W.Z.)
| | - Xinyi Zou
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China; (J.W.); (H.L.); (Z.S.); (X.Z.); (Z.Z.); (X.W.); (W.Z.)
| | - Zixuan Zhang
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China; (J.W.); (H.L.); (Z.S.); (X.Z.); (Z.Z.); (X.W.); (W.Z.)
| | - Xiaofeng Wei
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China; (J.W.); (H.L.); (Z.S.); (X.Z.); (Z.Z.); (X.W.); (W.Z.)
| | - Lanying Pan
- Shulan International Medical College, Zhejiang Shuren University, Hangzhou 310015, China
| | - Antony Stalin
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China;
| | - Wei Zhao
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China; (J.W.); (H.L.); (Z.S.); (X.Z.); (Z.Z.); (X.W.); (W.Z.)
| | - Yuan Chen
- Zhejiang Provincial Key Laboratory of Resources Protection and Innovation of Traditional Chinese Medicine, College of Food and Health, Zhejiang Agriculture and Forestry University, Hangzhou 311300, China; (J.W.); (H.L.); (Z.S.); (X.Z.); (Z.Z.); (X.W.); (W.Z.)
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Lee DS, Kim TH, Park H, Kang TC. Deregulation of Astroglial TASK-1 K+ Channel Decreases the Responsiveness to Perampanel-Induced AMPA Receptor Inhibition in Chronic Epilepsy Rats. Int J Mol Sci 2023; 24:ijms24065491. [PMID: 36982567 PMCID: PMC10049714 DOI: 10.3390/ijms24065491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2023] [Revised: 03/06/2023] [Accepted: 03/10/2023] [Indexed: 03/17/2023] Open
Abstract
Tandem of P domains in a weak inwardly rectifying K+ channel (TWIK)-related acid sensitive K+-1 channel (TASK-1) is activated under extracellular alkaline conditions (pH 7.2–8.2), which are upregulated in astrocytes (particularly in the CA1 region) of the hippocampi of patients with temporal lobe epilepsy and chronic epilepsy rats. Perampanel (PER) is a non-competitive α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) antagonist used for the treatment of focal seizures and primary generalized tonic–clonic seizures. Since AMPAR activation leads to extracellular alkaline shifts, it is likely that the responsiveness to PER in the epileptic hippocampus may be relevant to astroglial TASK-1 regulation, which has been unreported. In the present study, we found that PER ameliorated astroglial TASK-1 upregulation in responders (whose seizure activities were responsive to PER), but not non-responders (whose seizure activities were not responsive to PER), in chronic epilepsy rats. ML365 (a selective TASK-1 inhibitor) diminished astroglial TASK-1 expression and seizure duration in non-responders to PER. ML365 co-treatment with PER decreased spontaneous seizure activities in non-responders to PER. These findings suggest that deregulation of astroglial TASK-1 upregulation may participate in the responsiveness to PER, and that this may be a potential target to improve the efficacies of PER.
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Affiliation(s)
- Duk-Shin Lee
- Department of Anatomy and Neurobiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
- Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Tae-Hyun Kim
- Department of Anatomy and Neurobiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
- Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Hana Park
- Department of Anatomy and Neurobiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
- Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
| | - Tae-Cheon Kang
- Department of Anatomy and Neurobiology, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
- Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon 24252, Republic of Korea
- Correspondence: ; Tel.: +82-33-248-2524; Fax: +82-33-248-2525
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Fan X, Lu Y, Du G, Liu J. Advances in the Understanding of Two-Pore Domain TASK Potassium Channels and Their Potential as Therapeutic Targets. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27238296. [PMID: 36500386 PMCID: PMC9736439 DOI: 10.3390/molecules27238296] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/09/2022] [Accepted: 11/15/2022] [Indexed: 11/29/2022]
Abstract
TWIK-related acid-sensitive K+ (TASK) channels, including TASK-1, TASK-3, and TASK-5, are important members of the two-pore domain potassium (K2P) channel family. TASK-5 is not functionally expressed in the recombinant system. TASK channels are very sensitive to changes in extracellular pH and are active during all membrane potential periods. They are similar to other K2P channels in that they can create and use background-leaked potassium currents to stabilize resting membrane conductance and repolarize the action potential of excitable cells. TASK channels are expressed in both the nervous system and peripheral tissues, including excitable and non-excitable cells, and are widely engaged in pathophysiological phenomena, such as respiratory stimulation, pulmonary hypertension, arrhythmia, aldosterone secretion, cancers, anesthesia, neurological disorders, glucose homeostasis, and visual sensitivity. Therefore, they are important targets for innovative drug development. In this review, we emphasized the recent advances in our understanding of the biophysical properties, gating profiles, and biological roles of TASK channels. Given the different localization ranges and biologically relevant functions of TASK-1 and TASK-3 channels, the development of compounds that selectively target TASK-1 and TASK-3 channels is also summarized based on data reported in the literature.
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Affiliation(s)
- Xueming Fan
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu 610041, China
- Department of Anesthesiology, Guizhou Provincial People’s Hospital, Guiyang 550002, China
| | - Yongzhi Lu
- Guangdong Provincial Key Laboratory of Biocomputing, Guangzhou Institute of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510700, China
| | - Guizhi Du
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu 610041, China
- Correspondence: (G.D.); (J.L.)
| | - Jin Liu
- Laboratory of Anesthesia and Critical Care Medicine, National-Local Joint Engineering Research Center of Translational Medicine of Anesthesiology, Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu 610041, China
- Correspondence: (G.D.); (J.L.)
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6
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Turney TS, Li V, Brohawn SG. Structural Basis for pH-gating of the K + channel TWIK1 at the selectivity filter. Nat Commun 2022; 13:3232. [PMID: 35680900 PMCID: PMC9184524 DOI: 10.1038/s41467-022-30853-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Accepted: 05/20/2022] [Indexed: 11/11/2022] Open
Abstract
TWIK1 (K2P1.1, KCNK1) is a widely expressed pH-gated two-pore domain K+ channel (K2P) that contributes to cardiac rhythm generation and insulin release from pancreatic beta cells. TWIK1 displays unique properties among K2Ps including low basal activity and inhibition by extracellular protons through incompletely understood mechanisms. Here, we present cryo-EM structures of TWIK1 in lipid nanodiscs at high and low pH that reveal a previously undescribed gating mechanism at the K+ selectivity filter. At high pH, TWIK1 adopts an open conformation. At low pH, protonation of an extracellular histidine results in a cascade of conformational changes that close the channel by sealing the top of the selectivity filter, displacing the helical cap to block extracellular ion access pathways, and opening gaps for lipid block of the intracellular cavity. These data provide a mechanistic understanding for extracellular pH-gating of TWIK1 and illustrate how diverse mechanisms have evolved to gate the selectivity filter of K+ channels.
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Affiliation(s)
- Toby S Turney
- Biophysics Graduate Program, University of California Berkeley, Berkeley, CA, 94720, USA
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
- California Institute for Quantitative Biosciences (QB3), University of California Berkeley, Berkeley, CA, 94720, USA
| | - Vivian Li
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
- California Institute for Quantitative Biosciences (QB3), University of California Berkeley, Berkeley, CA, 94720, USA
| | - Stephen G Brohawn
- Department of Molecular & Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA.
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA.
- California Institute for Quantitative Biosciences (QB3), University of California Berkeley, Berkeley, CA, 94720, USA.
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7
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Kim JE, Kang TC. Blockade of TASK-1 Channel Improves the Efficacy of Levetiracetam in Chronically Epileptic Rats. Biomedicines 2022; 10:biomedicines10040787. [PMID: 35453538 PMCID: PMC9030960 DOI: 10.3390/biomedicines10040787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 03/21/2022] [Accepted: 03/26/2022] [Indexed: 11/29/2022] Open
Abstract
Tandem of P domains in a weak inwardly rectifying K+ channel (TWIK)-related acid sensitive K+-1 channel (TASK-1) is an outwardly rectifying K+ channel that acts in response to extracellular pH. TASK-1 is upregulated in the astrocytes (particularly in the CA1 region) of the hippocampi of patients with temporal lobe epilepsy and chronically epilepsy rats. Since levetiracetam (LEV) is an effective inhibitor for carbonic anhydrase, which has a pivotal role in buffering of extracellular pH, it is likely that the anti-epileptic action of LEV may be relevant to TASK-1 inhibition, which remains to be elusive. In the present study, we found that LEV diminished the upregulated TASK-1 expression in the CA1 astrocytes of responders (whose seizure activities were responsive to LEV), but not non-responders (whose seizure activities were not controlled by LEV) in chronically epileptic rats. ML365 (a selective TASK-1 inhibitor) only reduced seizure duration in LEV non-responders, concomitant with astroglial TASK-1 downregulation. Furthermore, ML365 co-treatment with LEV decreased the duration, frequency and severity of spontaneous seizures in non-responders to LEV. To the best of our knowledge, our findings suggest, for the first time, that the up-regulation of TASK-1 expression in CA1 astrocytes may be involved in refractory seizures in response to LEV. This may be a potential target to improve responsiveness to LEV.
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Affiliation(s)
| | - Tae-Cheon Kang
- Correspondence: ; Tel.: +82-33-248-2524; Fax: +82-33-248-2525
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8
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Abstract
K+ channels enable potassium to flow across the membrane with great selectivity. There are four K+ channel families: voltage-gated K (Kv), calcium-activated (KCa), inwardly rectifying K (Kir), and two-pore domain potassium (K2P) channels. All four K+ channels are formed by subunits assembling into a classic tetrameric (4x1P = 4P for the Kv, KCa, and Kir channels) or tetramer-like (2x2P = 4P for the K2P channels) architecture. These subunits can either be the same (homomers) or different (heteromers), conferring great diversity to these channels. They share a highly conserved selectivity filter within the pore but show different gating mechanisms adapted for their function. K+ channels play essential roles in controlling neuronal excitability by shaping action potentials, influencing the resting membrane potential, and responding to diverse physicochemical stimuli, such as a voltage change (Kv), intracellular calcium oscillations (KCa), cellular mediators (Kir), or temperature (K2P).
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9
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Varró A, Tomek J, Nagy N, Virág L, Passini E, Rodriguez B, Baczkó I. Cardiac transmembrane ion channels and action potentials: cellular physiology and arrhythmogenic behavior. Physiol Rev 2020; 101:1083-1176. [PMID: 33118864 DOI: 10.1152/physrev.00024.2019] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells and their underlying ionic mechanisms. It is therefore critical to further unravel the pathophysiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodeling) are discussed. The focus is on human-relevant findings obtained with clinical, experimental, and computational studies, given that interspecies differences make the extrapolation from animal experiments to human clinical settings difficult. Deepening the understanding of the diverse pathophysiology of human cellular electrophysiology will help in developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.
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Affiliation(s)
- András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - Jakub Tomek
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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10
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Alkalinization of the Synaptic Cleft during Excitatory Neurotransmission. J Neurosci 2020; 40:6267-6269. [PMID: 32801127 DOI: 10.1523/jneurosci.0914-20.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 06/20/2020] [Accepted: 07/05/2020] [Indexed: 11/21/2022] Open
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Pattison LA, Callejo G, St John Smith E. Evolution of acid nociception: ion channels and receptors for detecting acid. Philos Trans R Soc Lond B Biol Sci 2019; 374:20190291. [PMID: 31544616 PMCID: PMC6790391 DOI: 10.1098/rstb.2019.0291] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/27/2019] [Indexed: 12/13/2022] Open
Abstract
Nociceptors, i.e. sensory neurons tuned to detect noxious stimuli, are found in numerous phyla of the Animalia kingdom and are often polymodal, responding to a variety of stimuli, e.g. heat, cold, pressure and chemicals, such as acid. Owing to the ability of protons to have a profound effect on ionic homeostasis and damage macromolecular structures, it is no wonder that the ability to detect acid is conserved across many species. To detect changes in pH, nociceptors are equipped with an assortment of different acid sensors, some of which can detect mild changes in pH, such as the acid-sensing ion channels, proton-sensing G protein-coupled receptors and several two-pore potassium channels, whereas others, such as the transient receptor potential vanilloid 1 ion channel, require larger shifts in pH. This review will discuss the evolution of acid sensation and the different mechanisms by which nociceptors can detect acid. This article is part of the Theo Murphy meeting issue 'Evolution of mechanisms and behaviour important for pain'.
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Affiliation(s)
| | | | - Ewan St John Smith
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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12
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Yarishkin O, Phuong TTT, Križaj D. Trabecular Meshwork TREK-1 Channels Function as Polymodal Integrators of Pressure and pH. Invest Ophthalmol Vis Sci 2019; 60:2294-2303. [PMID: 31117121 PMCID: PMC6532698 DOI: 10.1167/iovs.19-26851] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Purpose The concentration of protons in the aqueous humor (AH) of the vertebrate eye is maintained close to blood pH; however, pathologic conditions and surgery may shift it by orders of magnitude. We investigated whether and how changes in extra- and intracellular pH affect the physiology and function of trabecular meshwork (TM) cells that regulate AH outflow. Methods Electrophysiology, in conjunction with pharmacology, gene knockdown, and optical recording, was used to track the pH dependence of transmembrane currents and mechanotransduction in primary and immortalized human TM cells. Results Extracellular acidification depolarized the resting membrane potential by inhibiting an outward K+-mediated current, whereas alkalinization hyperpolarized the cells and augmented the outward conductance. Intracellular acidification with sodium bicarbonate hyperpolarized TM cells, whereas removal of intracellular protons with ammonium chloride depolarized the membrane potential. The effects of extra- and intracellular acid and alkaline loading were abolished by quinine, a pan-selective inhibitor of two-pore domain potassium (K2P) channels, and suppressed by shRNA-mediated downregulation of the mechanosensitive K2P channel TREK-1. Extracellular acidosis suppressed, whereas alkalosis facilitated, the amplitude of the pressure-evoked TREK-1–mediated outward current. Conclusions These results demonstrate that TM mechanotransduction mediated by TREK-1 channels is profoundly sensitive to extra- and intracellular pH shifts. Intracellular acidification might modulate aqueous outflow and IOP by stimulating TREK-1 channels.
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Affiliation(s)
- Oleg Yarishkin
- Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, United States
| | - Tam T T Phuong
- Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, United States
| | - David Križaj
- Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, United States.,Department of Neurobiology and Anatomy, University of Utah, Salt Lake City, Utah, United States.,Department of Bioengineering, University of Utah, Salt Lake City, Utah, United States
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13
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Fischer RA, Roux AL, Wareham LK, Sappington RM. Pressure-dependent modulation of inward-rectifying K + channels: implications for cation homeostasis and K + dynamics in glaucoma. Am J Physiol Cell Physiol 2019; 317:C375-C389. [PMID: 31166711 DOI: 10.1152/ajpcell.00444.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Glaucoma is the leading cause of blindness worldwide, resulting from degeneration of retinal ganglion cells (RGCs), which form the optic nerve. Prior to structural degeneration, RGCs exhibit physiological deficits. Müller glia provide homeostatic regulation of ions that supports RGC physiology through a process called K+ siphoning. Recent studies suggest that several retinal conditions, including glaucoma, involve changes in the expression of K+ channels in Müller glia. To clarify whether glaucoma-related stressors directly alter expression and function of K+ channels in Müller glia, we examined changes in the expression of inwardly rectifying K+ (Kir) channels and two-pore domain (K2P) channels in response to elevated intraocular pressure (IOP) in vivo and in vitro in primary cultures of Müller glia exposed to elevated hydrostatic pressure. We then measured outcomes of cell health, cation homeostasis, and cation flux in Müller glia cultures. Transcriptome analysis in a murine model of microbead-induced glaucoma revealed pressure-dependent downregulation of Kir and K2P channels in vivo. Changes in the expression and localization of Kir and K2P channels in response to elevated pressure were also found in Müller glia in vitro. Finally, we found that elevated pressure compromises the plasma membrane of Müller glia and induces cation dyshomeostasis that involves changes in ion flux through cation channels. Pressure-induced changes in cation flux precede both cation dyshomeostasis and membrane compromise. Our findings have implications for Müller glia responses to pressure-related conditions, i.e., glaucoma, and identify cation dyshomeostasis as a potential contributor to electrophysiological impairment observed in RGCs of glaucomatous retina.
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Affiliation(s)
- Rachel A Fischer
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Abigail L Roux
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Lauren K Wareham
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Rebecca M Sappington
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee.,Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee.,Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee
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14
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Rinné S, Kiper AK, Vowinkel KS, Ramírez D, Schewe M, Bedoya M, Aser D, Gensler I, Netter MF, Stansfeld PJ, Baukrowitz T, Gonzalez W, Decher N. The molecular basis for an allosteric inhibition of K +-flux gating in K 2P channels. eLife 2019; 8:39476. [PMID: 30803485 PMCID: PMC6391080 DOI: 10.7554/elife.39476] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 02/06/2019] [Indexed: 01/05/2023] Open
Abstract
Two-pore-domain potassium (K2P) channels are key regulators of many physiological and pathophysiological processes and thus emerged as promising drug targets. As for other potassium channels, there is a lack of selective blockers, since drugs preferentially bind to a conserved binding site located in the central cavity. Thus, there is a high medical need to identify novel drug-binding sites outside the conserved lipophilic central cavity and to identify new allosteric mechanisms of channel inhibition. Here, we identified a novel binding site and allosteric inhibition mechanism, disrupting the recently proposed K+-flux gating mechanism of K2P channels, which results in an unusual voltage-dependent block of leak channels belonging to the TASK subfamily. The new binding site and allosteric mechanism of inhibition provide structural and mechanistic insights into the gating of TASK channels and the basis for the drug design of a new class of potent blockers targeting specific types of K2P channels.
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Affiliation(s)
- Susanne Rinné
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Aytug K Kiper
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Kirsty S Vowinkel
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - David Ramírez
- Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Talca, Chile.,Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Talca, Chile
| | - Marcus Schewe
- Institute of Physiology, University of Kiel, Kiel, Germany
| | - Mauricio Bedoya
- Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Talca, Chile
| | - Diana Aser
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Isabella Gensler
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Michael F Netter
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
| | - Phillip J Stansfeld
- Structural Bioinformatics and Computational Biochemistry Unit, Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | | | - Wendy Gonzalez
- Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Talca, Chile.,Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Talca, Talca, Chile
| | - Niels Decher
- Institute for Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, Marburg, Germany
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15
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Abstract
The trigeminal sensory nerve fiber branches supply afferent information from the skin and mucous membranes of the face and head and the oral cavity regarding information on temperature, touch, and pain. Under normal conditions, the trigeminal nerve serves to provide important information from nerve fibers and tissues using specialized receptors sensitive for irritant and painful stimuli. The current scientific consensus indicates that nerve endings responsible for chemical and thermal sensitivity of the skin and mucous membranes are the same nerves responsible for nociception. This "chemesthetic sense" allows many vertebrates to detect chemical agonists that induce sensations such as touch, burning, stinging, tingling, or changes in temperature. Research has been under way for many years to determine how exposure of the oral and/or nasal cavity to compounds that elicit pungent or irritant sensations can produce these sensations. In addition, these chemicals can alter other sensory information such as taste and smell to affect the flavor of foods and beverages. We now know that these 'chemesthetic molecules' are agonists of molecular receptors, which exist on primary afferent nerve fibers that innervate the orofacial area. However, under pathophysiologic conditions, over- or underexpression or activity of these receptors may lead to painful orotrigeminal syndromes. Some of these individual receptors are discussed in detail, including transient receptor potential channels and acid sensing ion channels, among others.
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Affiliation(s)
- Amanda H Klein
- Department of Pharmacy Practice and Pharmaceutical Sciences, University of Minnesota, Duluth, MN, United States. //
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16
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Soto E, Ortega-Ramírez A, Vega R. Protons as Messengers of Intercellular Communication in the Nervous System. Front Cell Neurosci 2018; 12:342. [PMID: 30364044 PMCID: PMC6191491 DOI: 10.3389/fncel.2018.00342] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 09/14/2018] [Indexed: 12/18/2022] Open
Abstract
In this review, evidence demonstrating that protons (H+) constitute a complex, regulated intercellular signaling mechanisms are presented. Given that pH is a strictly regulated variable in multicellular organisms, localized extracellular pH changes may constitute significant signals of cellular processes that occur in a cell or a group of cells. Several studies have demonstrated that the low pH of synaptic vesicles implies that neurotransmitter release is always accompanied by the co-release of H+ into the synaptic cleft, leading to transient extracellular pH shifts. Also, evidence has accumulated indicating that extracellular H+ concentration regulation is complex and implies a source of protons in a network of transporters, ion exchangers, and buffer capacity of the media that may finally establish the extracellular proton concentration. The activation of membrane transporters, increased production of CO2 and of metabolites, such as lactate, produce significant extracellular pH shifts in nano- and micro-domains in the central nervous system (CNS), constituting a reliable signal for intercellular communication. The acid sensing ion channels (ASIC) function as specific signal sensors of proton signaling mechanism, detecting subtle variations of extracellular H+ in a range varying from pH 5 to 8. The main question in relation to this signaling system is whether it is only synaptically restricted, or a volume modulator of neuron excitability. This signaling system may have evolved from a metabolic activity detection mechanism to a highly localized extracellular proton dependent communication mechanism. In this study, evidence showing the mechanisms of regulation of extracellular pH shifts and of the ASICs and its function in modulating the excitability in various systems is reviewed, including data and its role in synaptic neurotransmission, volume transmission and even segregated neurotransmission, leading to a reliable extracellular signaling mechanism.
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Affiliation(s)
- Enrique Soto
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
| | | | - Rosario Vega
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico
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17
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Pietak A, Levin M. Bioelectrical control of positional information in development and regeneration: A review of conceptual and computational advances. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 137:52-68. [PMID: 29626560 PMCID: PMC10464501 DOI: 10.1016/j.pbiomolbio.2018.03.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2018] [Revised: 03/23/2018] [Accepted: 03/26/2018] [Indexed: 12/16/2022]
Abstract
Positional information describes pre-patterns of morphogenetic substances that alter spatio-temporal gene expression to instruct development of growth and form. A wealth of recent data indicate bioelectrical properties, such as the transmembrane potential (Vmem), are involved as instructive signals in the spatiotemporal regulation of morphogenesis. However, the mechanistic relationships between Vmem and molecular positional information are only beginning to be understood. Recent advances in computational modeling are assisting in the development of comprehensive frameworks for mechanistically understanding how endogenous bioelectricity can guide anatomy in a broad range of systems. Vmem represents an extraordinarily strong electric field (∼1.0 × 106 V/m) active over the thin expanse of the plasma membrane, with the capacity to influence a variety of downstream molecular signaling cascades. Moreover, in multicellular networks, intercellular coupling facilitated by gap junction channels may induce directed, electrodiffusive transport of charged molecules between cells of the network to generate new positional information patterning possibilities and characteristics. Given the demonstrated role of Vmem in morphogenesis, here we review current understanding of how Vmem can integrate with molecular regulatory networks to control single cell state, and the unique properties bioelectricity adds to transport phenomena in gap junction-coupled cell networks to facilitate self-assembly of morphogen gradients and other patterns. Understanding how Vmem integrates with biochemical regulatory networks at the level of a single cell, and mechanisms through which Vmem shapes molecular positional information in multicellular networks, are essential for a deep understanding of body plan control in development, regeneration and disease.
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Affiliation(s)
| | - Michael Levin
- Allen Discovery Center at Tufts, USA; Center for Regenerative and Developmental Biology, Tufts University, Medford, MA, USA
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18
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Tsukamoto H, Higashi M, Motoki H, Watanabe H, Ganser C, Nakajo K, Kubo Y, Uchihashi T, Furutani Y. Structural properties determining low K + affinity of the selectivity filter in the TWIK1 K + channel. J Biol Chem 2018; 293:6969-6984. [PMID: 29545310 DOI: 10.1074/jbc.ra118.001817] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 03/14/2018] [Indexed: 11/06/2022] Open
Abstract
Canonical K+ channels are tetrameric and highly K+-selective, whereas two-pore-domain K+ (K2P) channels form dimers, but with a similar pore architecture. A two-pore-domain potassium channel TWIK1 (KCNK1 or K2P1) allows permeation of Na+ and other monovalent ions, resulting mainly from the presence of Thr-118 in the P1 domain. However, the mechanistic basis for this reduced selectivity is unclear. Using ion-exchange-induced difference IR spectroscopy, we analyzed WT TWIK1 and T118I (highly K+-selective) and L228F (substitution in the P2 domain) TWIK1 variants and found that in the presence of K+ ions, WT and both variants exhibit an amide-I band at 1680 cm-1 This band corresponds to interactions of the backbone carbonyls in the selectivity filter with K+, a feature very similar to that of the canonical K+ channel KcsA. Computational analysis indicated that the relatively high frequency for the amide-I band is well explained by impairment of hydrogen bond formation with water molecules. Moreover, concentration-dependent spectral changes indicated that the K+ affinity of the WT selectivity filter was much lower than those of the variants. Furthermore, only the variants displayed a higher frequency shift of the 1680-cm-1 band upon changes from K+ to Rb+ or Cs+ conditions. High-speed atomic force microscopy disclosed that TWIK1's surface morphology largely does not change in K+ and Na+ solutions. Our results reveal the local conformational changes of the TWIK1 selectivity filter and suggest that the amide-I bands may be useful "molecular fingerprints" for assessing the properties of other K+ channels.
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Affiliation(s)
- Hisao Tsukamoto
- From the Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, and.,Departments of Structural Molecular Science and
| | - Masahiro Higashi
- the Department of Chemistry, Biology and Marine Science, University of the Ryukyus, 1 Senbaru, Nishihara, Nakagami, Okinawa 903-0213
| | - Hideyoshi Motoki
- the Department of Chemistry, Biology and Marine Science, University of the Ryukyus, 1 Senbaru, Nishihara, Nakagami, Okinawa 903-0213
| | - Hiroki Watanabe
- the Department of Physics and Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, and
| | - Christian Ganser
- the Department of Physics and Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, and
| | - Koichi Nakajo
- the Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.,Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585
| | - Yoshihiro Kubo
- the Division of Biophysics and Neurobiology, Department of Molecular and Cellular Physiology, National Institute for Physiological Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.,Physiological Sciences, SOKENDAI (Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585
| | - Takayuki Uchihashi
- the Department of Physics and Structural Biology Research Center, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, and
| | - Yuji Furutani
- From the Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, and .,Departments of Structural Molecular Science and
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19
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Riegelhaupt PM, Tibbs GR, Goldstein PA. HCN and K 2P Channels in Anesthetic Mechanisms Research. Methods Enzymol 2018; 602:391-416. [PMID: 29588040 DOI: 10.1016/bs.mie.2018.01.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The ability of a diverse group of agents to produce general anesthesia has long been an area of intense speculation and investigation. Over the past century, we have seen a paradigm shift from proposing that the anesthetized state arises from nonspecific interaction of anesthetics with the lipid membrane to the recognition that the function of distinct, and identifiable, membrane-embedded proteins is dramatically altered in the presence of intravenous and inhaled agents. Among proteinaceous targets, metabotropic and ionotropic receptors garnered much of the attention over the last 30 years, and it is only relatively recently that voltage-gated ion channels have clearly and rigorously been shown to be important molecular targets. In this review, we will consider the experimental issues relevant to two important ion channel anesthetic targets, HCN and K2P.
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Affiliation(s)
| | - Gareth R Tibbs
- Weill Cornell Medical College, New York, NY, United States
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20
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Olschewski A, Veale EL, Nagy BM, Nagaraj C, Kwapiszewska G, Antigny F, Lambert M, Humbert M, Czirják G, Enyedi P, Mathie A. TASK-1 (KCNK3) channels in the lung: from cell biology to clinical implications. Eur Respir J 2017; 50:50/5/1700754. [PMID: 29122916 DOI: 10.1183/13993003.00754-2017] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 08/05/2017] [Indexed: 12/18/2022]
Abstract
TWIK-related acid-sensitive potassium channel 1 (TASK-1 encoded by KCNK3) belongs to the family of two-pore domain potassium channels. This gene subfamily is constitutively active at physiological resting membrane potentials in excitable cells, including smooth muscle cells, and has been particularly linked to the human pulmonary circulation. TASK-1 channels are sensitive to a wide array of physiological and pharmacological mediators that affect their activity such as unsaturated fatty acids, extracellular pH, hypoxia, anaesthetics and intracellular signalling pathways. Recent studies show that modulation of TASK-1 channels, either directly or indirectly by targeting their regulatory mechanisms, has the potential to control pulmonary arterial tone in humans. Furthermore, mutations in KCNK3 have been identified as a rare cause of both familial and idiopathic pulmonary arterial hypertension. This review summarises our current state of knowledge of the functional role of TASK-1 channels in the pulmonary circulation in health and disease, with special emphasis on current advancements in the field.
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Affiliation(s)
- Andrea Olschewski
- Ludwig Boltzmann Institute for Lung Vascular Research Graz, Graz, Austria .,Institute of Physiology, Medical University of Graz, Graz, Austria
| | - Emma L Veale
- Medway School of Pharmacy, University of Kent, Central Avenue, Chatham Maritime, UK
| | - Bence M Nagy
- Institute of Physiology, Medical University of Graz, Graz, Austria
| | - Chandran Nagaraj
- Ludwig Boltzmann Institute for Lung Vascular Research Graz, Graz, Austria.,Institute of Physiology, Medical University of Graz, Graz, Austria
| | - Grazyna Kwapiszewska
- Ludwig Boltzmann Institute for Lung Vascular Research Graz, Graz, Austria.,Institute of Physiology, Medical University of Graz, Graz, Austria
| | - Fabrice Antigny
- Univ. Paris-Sud, Faculté de Médecine, Kremlin-Bicêtre, France.,AP-HP, Centre de Référence de l'Hypertension Pulmonaire Sévère, Département Hospitalo-Universitaire (DHU) Thorax Innovation, Service de Pneumologie et Réanimation Respiratoire, Hôpital de Bicêtre, Le Kremlin-Bicêtre, France.,UMRS 999, INSERM and Univ. Paris-Sud, Laboratoire d'Excellence (LabEx) en Recherche sur le Médicament et l'Innovation Thérapeutique (LERMIT), Hôpital-Marie-Lannelongue, Le Plessis Robinson, France
| | - Mélanie Lambert
- Univ. Paris-Sud, Faculté de Médecine, Kremlin-Bicêtre, France.,AP-HP, Centre de Référence de l'Hypertension Pulmonaire Sévère, Département Hospitalo-Universitaire (DHU) Thorax Innovation, Service de Pneumologie et Réanimation Respiratoire, Hôpital de Bicêtre, Le Kremlin-Bicêtre, France.,UMRS 999, INSERM and Univ. Paris-Sud, Laboratoire d'Excellence (LabEx) en Recherche sur le Médicament et l'Innovation Thérapeutique (LERMIT), Hôpital-Marie-Lannelongue, Le Plessis Robinson, France
| | - Marc Humbert
- Univ. Paris-Sud, Faculté de Médecine, Kremlin-Bicêtre, France.,AP-HP, Centre de Référence de l'Hypertension Pulmonaire Sévère, Département Hospitalo-Universitaire (DHU) Thorax Innovation, Service de Pneumologie et Réanimation Respiratoire, Hôpital de Bicêtre, Le Kremlin-Bicêtre, France.,UMRS 999, INSERM and Univ. Paris-Sud, Laboratoire d'Excellence (LabEx) en Recherche sur le Médicament et l'Innovation Thérapeutique (LERMIT), Hôpital-Marie-Lannelongue, Le Plessis Robinson, France
| | - Gábor Czirják
- Dept of Physiology, Semmelweis University, Budapest, Hungary
| | - Péter Enyedi
- Dept of Physiology, Semmelweis University, Budapest, Hungary
| | - Alistair Mathie
- Medway School of Pharmacy, University of Kent, Central Avenue, Chatham Maritime, UK
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21
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Decher N, Ortiz-Bonnin B, Friedrich C, Schewe M, Kiper AK, Rinné S, Seemann G, Peyronnet R, Zumhagen S, Bustos D, Kockskämper J, Kohl P, Just S, González W, Baukrowitz T, Stallmeyer B, Schulze-Bahr E. Sodium permeable and "hypersensitive" TREK-1 channels cause ventricular tachycardia. EMBO Mol Med 2017; 9:403-414. [PMID: 28242754 PMCID: PMC5376757 DOI: 10.15252/emmm.201606690] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In a patient with right ventricular outflow tract (RVOT) tachycardia, we identified a heterozygous point mutation in the selectivity filter of the stretch-activated K2P potassium channel TREK-1 (KCNK2 or K2P2.1). This mutation introduces abnormal sodium permeability to TREK-1. In addition, mutant channels exhibit a hypersensitivity to stretch-activation, suggesting that the selectivity filter is directly involved in stretch-induced activation and desensitization. Increased sodium permeability and stretch-sensitivity of mutant TREK-1 channels may trigger arrhythmias in areas of the heart with high physical strain such as the RVOT We present a pharmacological strategy to rescue the selectivity defect of the TREK-1 pore. Our findings provide important insights for future studies of K2P channel stretch-activation and the role of TREK-1 in mechano-electrical feedback in the heart.
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Affiliation(s)
- Niels Decher
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, Marburg, Germany
| | - Beatriz Ortiz-Bonnin
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, Marburg, Germany
| | - Corinna Friedrich
- Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Münster, Germany
| | - Marcus Schewe
- Institute of Physiology, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Aytug K Kiper
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, Marburg, Germany
| | - Susanne Rinné
- Institute of Physiology and Pathophysiology, Vegetative Physiology, Philipps-University of Marburg, Marburg, Germany
| | - Gunnar Seemann
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Medical Center - University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Medical Center - University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Sven Zumhagen
- Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Münster, Germany
| | - Daniel Bustos
- Center for Bioinformatics and Molecular Simulation, University of Talca, Talca, Chile
| | - Jens Kockskämper
- Institute of Pharmacology and Clinical Pharmacy, Biochemical and Pharmacological Center (BPC) Philipps-University of Marburg, Marburg, Germany
| | - Peter Kohl
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Medical Center - University of Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Steffen Just
- Molecular Cardiology, University Hospital Ulm, Ulm, Germany
| | - Wendy González
- Center for Bioinformatics and Molecular Simulation, University of Talca, Talca, Chile
| | - Thomas Baukrowitz
- Institute of Physiology, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Birgit Stallmeyer
- Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Münster, Germany
| | - Eric Schulze-Bahr
- Department of Cardiovascular Medicine, Institute for Genetics of Heart Diseases (IfGH), University Hospital Münster, Münster, Germany
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22
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Oakes V, Furini S, Pryde D, Domene C. Exploring the Dynamics of the TWIK-1 Channel. Biophys J 2017; 111:775-784. [PMID: 27558721 PMCID: PMC5002071 DOI: 10.1016/j.bpj.2016.07.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 05/13/2016] [Accepted: 07/11/2016] [Indexed: 01/02/2023] Open
Abstract
Potassium channels in the two-pore domain family (K2P) have various structural attributes that differ from those of other K(+) channels, including a dimeric assembly constituted of nonidentical domains and an expansive extracellular cap. Crystallization of the prototypical K2P channel, TWIK-1, finally revealed the structure of these characteristics in atomic detail, allowing computational studies to be undertaken. In this study, we performed molecular-dynamics simulations for a cumulative time of ∼1 μs to discern the mechanism of ion transport throughout TWIK-1. We observed the free passage of ions beneath the extracellular cap and identified multiple high-occupancy sites in close proximity to charged residues on the protein surface. Despite the overall topological similarity of the x-ray structure of the selectivity filter to other K(+) channels, the structure diverges significantly in molecular-dynamics simulations as a consequence of nonconserved residues in both pore domains contributing to the selectivity filter (T118 and L228). The behavior of such residues has been linked to channel inactivation and the phenomenon of dynamic selectivity, where TWIK-1 displays robust Na(+) inward flux in response to subphysiological K(+) concentrations.
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Affiliation(s)
- Victoria Oakes
- Department of Chemistry, King's College London, London, United Kingdom
| | - Simone Furini
- Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - David Pryde
- Worldwide Medicinal Chemistry, Pfizer Neuroscience and Pain Research Unit, Cambridge, United Kingdom
| | - Carmen Domene
- Department of Chemistry, King's College London, London, United Kingdom; Chemistry Research Laboratory, Mansfield Road, University of Oxford, Oxford, United Kingdom.
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23
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Decher N, Kiper AK, Rinné S. Stretch-activated potassium currents in the heart: Focus on TREK-1 and arrhythmias. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 130:223-232. [PMID: 28526352 DOI: 10.1016/j.pbiomolbio.2017.05.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 05/09/2017] [Accepted: 05/15/2017] [Indexed: 12/26/2022]
Abstract
This review focuses on the role and the molecular candidates of the cardiac stretch-activated potassium current (SAK). The functional properties of the two-pore domain potassium (K2P) channel TREK-1, a major candidate for the cardiac SAK, are analyzed and the molecular mechanism of stretch-activation in K2P potassium channels is discussed. Furthermore, the functional modulation of TREK-1 by different cardiac interaction partners, as well as evidence for the functional role of the stretch-dependent TREK-1 and its putative subunits in the heart is reviewed. In addition, we summarize the recent evidence that TREK-1 is involved in the pathogenesis of human cardiac arrhythmias.
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Affiliation(s)
- Niels Decher
- Institute for Physiology and Pathophysiology, AG Vegetative Physiology, Deutschhausstrasse 1-2, 35037 Marburg, Germany.
| | - Aytug K Kiper
- Institute for Physiology and Pathophysiology, AG Vegetative Physiology, Deutschhausstrasse 1-2, 35037 Marburg, Germany
| | - Susanne Rinné
- Institute for Physiology and Pathophysiology, AG Vegetative Physiology, Deutschhausstrasse 1-2, 35037 Marburg, Germany
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24
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Mazzone GL, Veeraraghavan P, Gonzalez-Inchauspe C, Nistri A, Uchitel OD. ASIC channel inhibition enhances excitotoxic neuronal death in an in vitro model of spinal cord injury. Neuroscience 2016; 343:398-410. [PMID: 28003157 DOI: 10.1016/j.neuroscience.2016.12.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 11/23/2016] [Accepted: 12/04/2016] [Indexed: 01/06/2023]
Abstract
In the spinal cord high extracellular glutamate evokes excitotoxic damage with neuronal loss and severe locomotor impairment. During the cell dysfunction process, extracellular pH becomes acid and may activate acid-sensing ion channels (ASICs) which could be important contributors to neurodegenerative pathologies. Our previous studies have shown that transient application of the glutamate analog kainate (KA) evokes delayed excitotoxic death of spinal neurons, while white matter is mainly spared. The present goal was to enquire if ASIC channels modulated KA damage in relation to locomotor network function and cell death. Mouse spinal cord slices were treated with KA (0.01 or 0.1mM) for 1h, and then washed out for 24h prior to analysis. RT-PCR results showed that KA (at 0.01mM concentration that is near-threshold for damage) increased mRNA expression of ASIC1a, ASIC1b, ASIC2 and ASIC3, an effect reversed by the ASIC inhibitor 4',6-diamidino-2-phenylindole (DAPI). A KA neurotoxic dose (0.1mM) reduced ASIC1a and ASIC2 expression. Cell viability assays demonstrated KA-induced large damage in spinal slices from mice with ASIC1a gene ablation. Likewise, immunohistochemistry indicated significant neuronal loss when KA was followed by the ASIC inhibitors DAPI or amiloride. Electrophysiological recording from ventral roots of isolated spinal cords showed that alternating oscillatory cycles were slowed down by 0.01mMKA, and intensely inhibited by subsequently applied DAPI or amiloride. Our data suggest that early rise in ASIC expression and function counteracted deleterious effects on spinal networks by raising the excitotoxicity threshold, a result with potential implications for improving neuroprotection.
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Affiliation(s)
- Graciela L Mazzone
- Laboratorios de Investigación aplicada en Neurociencias (LIAN) - Fundación para la Lucha conntra las Enfermedades Neurológicas de la Infancia (FLENI), CONICET, Buenos Aires, Argentina.
| | | | - Carlota Gonzalez-Inchauspe
- Instituto de Fisiología, Biología molecular y Neurociencias, CONICET, Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
| | - Andrea Nistri
- Neuroscience Department, International School for Advanced Studies (SISSA), Trieste, Italy; Spinal Person Injury Neurorehabilitation Applied Laboratory (SPINAL), Istituto di Medicina Fisica e Riabilitazione, Udine, Italy
| | - Osvaldo D Uchitel
- Instituto de Fisiología, Biología molecular y Neurociencias, CONICET, Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina
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25
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Abstract
Despite the epidemiological scale of atrial fibrillation, current treatment strategies are of limited efficacy and safety. Ideally, novel drugs should specifically correct the pathophysiological mechanisms responsible for atrial fibrillation with no other cardiac or extracardiac actions. Atrial-selective drugs are directed toward cellular targets with sufficiently different characteristics in atria and ventricles to modify only atrial function. Several potassium (K+) channels with either predominant expression in atria or distinct electrophysiological properties in atria and ventricles can serve as atrial-selective drug targets. These channels include the ultra-rapidly activating, delayed outward-rectifying Kv1.5 channel conducting IKur, the acetylcholine-activated inward-rectifying Kir3.1/Kir3.4 channel conducting IK,ACh, the Ca2+-activated K+ channels of small conductance (SK) conducting ISK, and the two pore domain K+ (K2P) channels TWIK-1, TASK-1 and TASK-3 that are responsible for voltage-independent background currents ITWIK-1, ITASK-1, and ITASK-3. Here, we briefly review the characteristics of these K+ channels and their roles in atrial fibrillation. The antiarrhythmic potential of drugs targeting the described channels is discussed as well as their putative value in treatment of atrial fibrillation.
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Affiliation(s)
- Ursula Ravens
- Institute of Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg, Germany; Department of Cardiology and Angiology I, University Heart Center Freiburg-Bad Krozingen, Freiburg, Germany; Department of Physiology, Medical Faculty Carl-Gustav-Carus, TU Dresden, Dresden, Germany.
| | - Katja E Odening
- Institute of Experimental Cardiovascular Medicine, University Heart Center Freiburg-Bad Krozingen, Freiburg, Germany; Department of Cardiology and Angiology I, University Heart Center Freiburg-Bad Krozingen, Freiburg, Germany
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26
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Niemeyer MI, Cid LP, González W, Sepúlveda FV. Gating, Regulation, and Structure in K2P K+ Channels: In Varietate Concordia? Mol Pharmacol 2016; 90:309-17. [DOI: 10.1124/mol.116.103895] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 05/31/2016] [Indexed: 11/22/2022] Open
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27
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Du Y, Kiyoshi CM, Wang Q, Wang W, Ma B, Alford CC, Zhong S, Wan Q, Chen H, Lloyd EE, Bryan RM, Zhou M. Genetic Deletion of TREK-1 or TWIK-1/TREK-1 Potassium Channels does not Alter the Basic Electrophysiological Properties of Mature Hippocampal Astrocytes In Situ. Front Cell Neurosci 2016; 10:13. [PMID: 26869883 PMCID: PMC4738265 DOI: 10.3389/fncel.2016.00013] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 01/14/2016] [Indexed: 01/03/2023] Open
Abstract
We have recently shown that a linear current-to-voltage (I-V) relationship of membrane conductance (passive conductance) reflects the intrinsic property of K+ channels in mature astrocytes. While passive conductance is known to underpin a highly negative and stable membrane potential (VM) essential for the basic homeostatic function of astrocytes, a complete repertoire of the involved K+ channels remains elusive. TREK-1 two-pore domain K+ channel (K2P) is highly expressed in astrocytes, and covalent association of TREK-1 with TWIK-1, another highly expressed astrocytic K2P, has been reported as a mechanism underlying the trafficking of heterodimer TWIK-1/TREK-1 channel to the membrane and contributing to astrocyte passive conductance. To decipher the individual contribution of TREK-1 and address whether the appearance of passive conductance is conditional to the co-expression of TWIK-1/TREK-1 in astrocytes, TREK-1 single and TWIK-1/TREK-1 double gene knockout mice were used in the present study. The relative quantity of mRNA encoding other astrocyte K+ channels, such as Kir4.1, Kir5.1, and TREK-2, was not altered in these gene knockout mice. Whole-cell recording from hippocampal astrocytes in situ revealed no detectable changes in astrocyte passive conductance, VM, or membrane input resistance (Rin) in either kind of gene knockout mouse. Additionally, TREK-1 proteins were mainly located in the intracellular compartments of the hippocampus. Altogether, genetic deletion of TREK-1 alone or together with TWIK-1 produced no obvious alteration in the basic electrophysiological properties of hippocampal astrocytes. Thus, future research focusing on other K+ channels may shed light on this long-standing and important question in astrocyte physiology.
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Affiliation(s)
- Yixing Du
- Department of Neuroscience, The Ohio State University Wexner Medical CenterColumbus, OH, USA; Department of Neurology, The First Affiliated Hospital of Nanjing Medical UniversityNanjing, China
| | - Conrad M Kiyoshi
- Department of Neuroscience, The Ohio State University Wexner Medical Center Columbus, OH, USA
| | - Qi Wang
- Department of Neuroscience, The Ohio State University Wexner Medical CenterColumbus, OH, USA; Department of Neurology, Meitan General HospitalXibahe Nanli, Beijing, China
| | - Wei Wang
- Department of Physiology, Institute of Brain Research, School of Basic Medicine, Huazhong University of Science and Technology Wuhan, China
| | - Baofeng Ma
- Department of Neuroscience, The Ohio State University Wexner Medical Center Columbus, OH, USA
| | - Catherine C Alford
- Department of Neuroscience, The Ohio State University Wexner Medical Center Columbus, OH, USA
| | - Shiying Zhong
- Department of Neuroscience, The Ohio State University Wexner Medical Center Columbus, OH, USA
| | - Qi Wan
- Department of Neurology, The First Affiliated Hospital of Nanjing Medical University Nanjing, China
| | - Haijun Chen
- Department of Biological Science, University at Albany, State University of New York Albany, NY, USA
| | - Eric E Lloyd
- Department of Anesthesiology, Baylor College of Medicine Houston, TX, USA
| | - Robert M Bryan
- Department of Anesthesiology, Baylor College of Medicine Houston, TX, USA
| | - Min Zhou
- Department of Neuroscience, The Ohio State University Wexner Medical Center Columbus, OH, USA
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28
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Chen H, Zuo D, Zhang J, Zhou M, Ma L. Classification of 2-pore domain potassium channels based on rectification under quasi-physiological ionic conditions. Channels (Austin) 2015; 8:503-8. [PMID: 25616686 DOI: 10.4161/19336950.2014.973779] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
It is generally expected that 2-pore domain K(+) (K2P) channels are open or outward rectifiers in asymmetric physiological K(+) gradients, following the Goldman-Hodgkin-Katz (GHK) current equation. Although cloned K2P channels have been extensively studied, their current-voltage (I-V) relationships are not precisely characterized and previous definitions are contradictory. Here we study all the functional channels from 6 mammalian K2P subfamilies in transfected Chinese hamster ovary cells with patch-clamp technique, and examine whether their I-V relationships are described by the GHK current equation. K2P channels display 2 distinct types of I-V curves in asymmetric physiological K(+) gradients. Two K2P isoforms in the TWIK subfamily conduct large inward K(+) currents and have a nearly linear I-V curve. Ten isoforms from 5 other K2P subfamilies conduct small inward K(+) currents and exhibit open rectification, but fits with the GHK current equation cannot precisely reveal the differences in rectification among K2P channels. The Rectification Index, a ratio of limiting I-V slopes for outward and inward currents, is used to quantitatively describe open rectification of each K2P isoform, which is previously qualitatively defined as strong or weak open rectification. These results systematically and precisely classify K2P channels and suggest that TWIK K(+) channels have a unique feature in regulating cellular function.
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Affiliation(s)
- Haijun Chen
- a Department of Biological Sciences ; University at Albany; State University of New York ; Albany , NY USA
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29
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Ehling P, Bittner S, Meuth SG, Budde T. TASK, TREK & Co.: a mutable potassium channel family for diverse tasks in the brain. ACTA ACUST UNITED AC 2015. [DOI: 10.1007/s13295-015-0007-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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30
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Bandulik S, Tauber P, Lalli E, Barhanin J, Warth R. Two-pore domain potassium channels in the adrenal cortex. Pflugers Arch 2015; 467:1027-42. [PMID: 25339223 PMCID: PMC4428839 DOI: 10.1007/s00424-014-1628-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 10/02/2014] [Accepted: 10/03/2014] [Indexed: 12/31/2022]
Abstract
The physiological control of steroid hormone secretion from the adrenal cortex depends on the function of potassium channels. The "two-pore domain K(+) channels" (K2P) TWIK-related acid sensitive K(+) channel 1 (TASK1), TASK3, and TWIK-related K(+) channel 1 (TREK1) are strongly expressed in adrenocortical cells. They confer a background K(+) conductance to these cells which is important for the K(+) sensitivity as well as for angiotensin II and adrenocorticotropic hormone-dependent stimulation of aldosterone and cortisol synthesis. Mice with single deletions of the Task1 or Task3 gene as well as Task1/Task3 double knockout mice display partially autonomous aldosterone synthesis. It appears that TASK1 and TASK3 serve different functions: TASK1 affects cell differentiation and prevents expression of aldosterone synthase in the zona fasciculata, while TASK3 controls aldosterone secretion in glomerulosa cells. TREK1 is involved in the regulation of cortisol secretion in fasciculata cells. These data suggest that a disturbed function of K2P channels could contribute to adrenocortical pathologies in humans.
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Affiliation(s)
- Sascha Bandulik
- Medical Cell Biology, University of Regensburg, Universitaetsstrasse 31, 93053, Regensburg, Germany,
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31
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Dadi PK, Luo B, Vierra NC, Jacobson DA. TASK-1 Potassium Channels Limit Pancreatic α-Cell Calcium Influx and Glucagon Secretion. MOLECULAR ENDOCRINOLOGY (BALTIMORE, MD.) 2015. [PMID: 25849724 DOI: 10.1210/me.2014‐1321] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Glucose regulation of pancreatic α-cell Ca(2+) entry through voltage-dependent Ca(2+) channels is essential for normal glucagon secretion and becomes defective during the pathogenesis of diabetes mellitus. The 2-pore domain K(+) channel, TWIK-related acid-sensitive K(+) channel 1 (TASK-1), is an important modulator of membrane voltage and Ca(2+) entry. However, its role in α-cells has not been determined. Therefore, we addressed how TASK-1 channels regulate α-cell electrical activity, Ca(2+) entry, and glucagon secretion. We find that TASK-1 channels expressed in human and rodent α-cells are blocked by the TASK-1 channel inhibitor A1899. Alpha-cell 2-pore domain K(+) currents were also significantly reduced after ablation of mouse α-cell TASK-1 channels. Inhibition of TASK-1 channels with A1899 caused plasma membrane potential depolarization in both human and mouse α-cells, which resulted in increased electrical excitability. Moreover, ablation of α-cell TASK-1 channels increased α-cell electrical excitability under elevated glucose (11 mM) conditions compared with control α-cells. This resulted in significantly elevated α-cell Ca(2+) influx when TASK-1 channels were inhibited in the presence of high glucose (14 mM). However, there was an insignificant change in α-cell Ca(2+) influx after TASK-1 inhibition in low glucose (1 mM). Glucagon secretion from mouse and human islets was also elevated specifically in high (11 mM) glucose after acute TASK-1 inhibition. Interestingly, mice deficient for α-cell TASK-1 showed improvements in both glucose inhibition of glucagon secretion and glucose tolerance, which resulted from the chronic loss of α-cell TASK-1 currents. Therefore, these data suggest an important role for TASK-1 channels in limiting α-cell excitability and glucagon secretion during glucose stimulation.
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Affiliation(s)
- Prasanna K Dadi
- Department of Molecular Physiology and Biophysics (P.K.D., N.C.V., D.A.J.), Vanderbilt University, Nashville, Tennessee 37232-0615; and University of Oklahoma College of Medicine (B.L.), Oklahoma City, Oklahoma 73104-5042
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32
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Dadi PK, Luo B, Vierra NC, Jacobson DA. TASK-1 Potassium Channels Limit Pancreatic α-Cell Calcium Influx and Glucagon Secretion. Mol Endocrinol 2015; 29:777-87. [PMID: 25849724 DOI: 10.1210/me.2014-1321] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Glucose regulation of pancreatic α-cell Ca(2+) entry through voltage-dependent Ca(2+) channels is essential for normal glucagon secretion and becomes defective during the pathogenesis of diabetes mellitus. The 2-pore domain K(+) channel, TWIK-related acid-sensitive K(+) channel 1 (TASK-1), is an important modulator of membrane voltage and Ca(2+) entry. However, its role in α-cells has not been determined. Therefore, we addressed how TASK-1 channels regulate α-cell electrical activity, Ca(2+) entry, and glucagon secretion. We find that TASK-1 channels expressed in human and rodent α-cells are blocked by the TASK-1 channel inhibitor A1899. Alpha-cell 2-pore domain K(+) currents were also significantly reduced after ablation of mouse α-cell TASK-1 channels. Inhibition of TASK-1 channels with A1899 caused plasma membrane potential depolarization in both human and mouse α-cells, which resulted in increased electrical excitability. Moreover, ablation of α-cell TASK-1 channels increased α-cell electrical excitability under elevated glucose (11 mM) conditions compared with control α-cells. This resulted in significantly elevated α-cell Ca(2+) influx when TASK-1 channels were inhibited in the presence of high glucose (14 mM). However, there was an insignificant change in α-cell Ca(2+) influx after TASK-1 inhibition in low glucose (1 mM). Glucagon secretion from mouse and human islets was also elevated specifically in high (11 mM) glucose after acute TASK-1 inhibition. Interestingly, mice deficient for α-cell TASK-1 showed improvements in both glucose inhibition of glucagon secretion and glucose tolerance, which resulted from the chronic loss of α-cell TASK-1 currents. Therefore, these data suggest an important role for TASK-1 channels in limiting α-cell excitability and glucagon secretion during glucose stimulation.
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Affiliation(s)
- Prasanna K Dadi
- Department of Molecular Physiology and Biophysics (P.K.D., N.C.V., D.A.J.), Vanderbilt University, Nashville, Tennessee 37232-0615; and University of Oklahoma College of Medicine (B.L.), Oklahoma City, Oklahoma 73104-5042
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33
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Renigunta V, Schlichthörl G, Daut J. Much more than a leak: structure and function of K₂p-channels. Pflugers Arch 2015; 467:867-94. [PMID: 25791628 DOI: 10.1007/s00424-015-1703-7] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 03/09/2015] [Indexed: 11/27/2022]
Abstract
Over the last decade, we have seen an enormous increase in the number of experimental studies on two-pore-domain potassium channels (K2P-channels). The collection of reviews and original articles compiled for this special issue of Pflügers Archiv aims to give an up-to-date summary of what is known about the physiology and pathophysiology of K2P-channels. This introductory overview briefly describes the structure of K2P-channels and their function in different organs. Its main aim is to provide some background information for the 19 reviews and original articles of this special issue of Pflügers Archiv. It is not intended to be a comprehensive review; instead, this introductory overview focuses on some unresolved questions and controversial issues, such as: Do K2P-channels display voltage-dependent gating? Do K2P-channels contribute to the generation of action potentials? What is the functional role of alternative translation initiation? Do K2P-channels have one or two or more gates? We come to the conclusion that we are just beginning to understand the extremely complex regulation of these fascinating channels, which are often inadequately described as 'leak channels'.
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Affiliation(s)
- Vijay Renigunta
- Institute of Physiology and Pathophysiology, Marburg University, 35037, Marburg, Germany
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34
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Sepúlveda FV, Pablo Cid L, Teulon J, Niemeyer MI. Molecular aspects of structure, gating, and physiology of pH-sensitive background K2P and Kir K+-transport channels. Physiol Rev 2015; 95:179-217. [PMID: 25540142 DOI: 10.1152/physrev.00016.2014] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
K(+) channels fulfill roles spanning from the control of excitability to the regulation of transepithelial transport. Here we review two groups of K(+) channels, pH-regulated K2P channels and the transport group of Kir channels. After considering advances in the molecular aspects of their gating based on structural and functional studies, we examine their participation in certain chosen physiological and pathophysiological scenarios. Crystal structures of K2P and Kir channels reveal rather unique features with important consequences for the gating mechanisms. Important tasks of these channels are discussed in kidney physiology and disease, K(+) homeostasis in the brain by Kir channel-equipped glia, and central functions in the hearing mechanism in the inner ear and in acid secretion by parietal cells in the stomach. K2P channels fulfill a crucial part in central chemoreception probably by virtue of their pH sensitivity and are central to adrenal secretion of aldosterone. Finally, some unorthodox behaviors of the selectivity filters of K2P channels might explain their normal and pathological functions. Although a great deal has been learned about structure, molecular details of gating, and physiological functions of K2P and Kir K(+)-transport channels, this has been only scratching at the surface. More molecular and animal studies are clearly needed to deepen our knowledge.
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Affiliation(s)
- Francisco V Sepúlveda
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - L Pablo Cid
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - Jacques Teulon
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
| | - María Isabel Niemeyer
- Centro de Estudios Científicos, Valdivia, Chile; UPMC Université Paris 06, Team 3, Paris, France; and Institut National de la Santé et de la Recherche Médicale, UMR_S 1138, Paris, France
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35
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Feliciangeli S, Chatelain FC, Bichet D, Lesage F. The family of K2P channels: salient structural and functional properties. J Physiol 2015; 593:2587-603. [PMID: 25530075 DOI: 10.1113/jphysiol.2014.287268] [Citation(s) in RCA: 148] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 12/10/2014] [Indexed: 12/11/2022] Open
Abstract
Potassium channels participate in many biological functions, from ion homeostasis to generation and modulation of the electrical membrane potential. They are involved in a large variety of diseases. In the human genome, 15 genes code for K(+) channels with two pore domains (K2P ). These channels form dimers of pore-forming subunits that produce background conductances finely regulated by a range of natural and chemical effectors, including signalling lipids, temperature, pressure, pH, antidepressants and volatile anaesthetics. Since the cloning of TWIK1, the prototypical member of this family, a lot of work has been carried out on their structure and biology. These studies are still in progress, but data gathered so far show that K2P channels are central players in many processes, including ion homeostasis, hormone secretion, cell development and excitability. A growing number of studies underline their implication in physiopathological mechanisms, such as vascular and pulmonary hypertension, cardiac arrhythmias, nociception, neuroprotection and depression. This review gives a synthetic view of the most noticeable features of these channels.
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Affiliation(s)
- Sylvain Feliciangeli
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
| | - Frank C Chatelain
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
| | - Delphine Bichet
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
| | - Florian Lesage
- LabEx ICST, Institut de Pharmacologie Moléculaire et Cellulaire, CNRS and Université de Nice-Sophia Antipolis, 660 Route des Lucioles, 06560, Valbonne, France
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36
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The role of acid-sensitive two-pore domain potassium channels in cardiac electrophysiology: focus on arrhythmias. Pflugers Arch 2014; 467:1055-67. [PMID: 25404566 DOI: 10.1007/s00424-014-1637-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 10/14/2014] [Accepted: 10/21/2014] [Indexed: 10/24/2022]
Abstract
The current kinetics of two-pore domain potassium (K2P) channels resemble those of the steady-state K(+) currents being active during the plateau phase of cardiac action potentials. Recent studies support that K2P channels contribute to these cardiac currents and thereby influence action potential duration in the heart. Ten of the 15 K2P channels present in the human genome are sensitive to variations of the extracellular and/or intracellular pH value. This review focuses on a set of K2P channels which are inhibited by extracellular protons, including the subgroup of tandem of P domains in a weak inward-rectifying K(+) (TWIK)-related acid-sensitive potassium (TASK) and TWIK-related alkaline-activated K(+) (TALK) channels. The role of TWIK-1 in the heart is also discussed since, after successful expression, an extracellular pH dependence, similar to that of TASK-1, was described as a hallmark of TWIK-1. The expression profile in cardiac tissue of different species and the functional data in the heart are summarized. The distinct role of the different acid-sensitive K2P channels in cardiac electrophysiology, inherited forms of arrhythmias and pharmacology, and their role as drug targets is currently emerging and is the subject of this review.
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37
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López-Cayuqueo KI, Peña-Münzenmayer G, Niemeyer MI, Sepúlveda FV, Cid LP. TASK-2 K₂p K⁺ channel: thoughts about gating and its fitness to physiological function. Pflugers Arch 2014; 467:1043-53. [PMID: 25315981 DOI: 10.1007/s00424-014-1627-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 10/02/2014] [Accepted: 10/03/2014] [Indexed: 01/08/2023]
Abstract
TASK-2 (K2P5) was one of the earliest members of the K2P two-pore, four transmembrane domain K(+) channels to be identified. TASK-2 gating is controlled by changes in both extra- and intracellular pH through separate sensors: arginine 224 and lysine 245, located at the extra- and intracellular ends of transmembrane domain 4. TASK-2 is inhibited by a direct effect of CO2 and is regulated by and interacts with G protein subunits. TASK-2 takes part in regulatory adjustments and is a mediator in the chemoreception process in neurons of the retrotrapezoid nucleus where its pHi sensitivity could be important in regulating excitability and therefore signalling of the O2/CO2 status. Extracellular pH increases brought about by HCO3 (-) efflux from proximal tubule epithelial cells have been proposed to couple to TASK-2 activation to maintain electrochemical gradients favourable to HCO3 (-) reabsorption. We demonstrate that, as suspected previously, TASK-2 is expressed at the basolateral membrane of the same proximal tubule cells that express apical membrane Na(+)-H(+)-exchanger NHE-3 and basolateral membrane Na(+)-HCO3 (-) cotransporter NBCe1-A, the main components of the HCO3 (-) transport machinery. We also discuss critically the mechanism by which TASK-2 is modulated and impacts the process of HCO3 (-) reclaim by the proximal tubule epithelium, concluding that more than a mere shift in extracellular pH is probably involved.
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Affiliation(s)
- Karen I López-Cayuqueo
- Centro de Estudios Científicos (CECs), Avenida Arturo Prat 514, 5110466, Valdivia, Chile
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Dadi PK, Vierra NC, Jacobson DA. Pancreatic β-cell-specific ablation of TASK-1 channels augments glucose-stimulated calcium entry and insulin secretion, improving glucose tolerance. Endocrinology 2014; 155:3757-68. [PMID: 24932805 PMCID: PMC4164933 DOI: 10.1210/en.2013-2051] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Calcium entry through voltage-dependent Ca(2+) channels (VDCCs) is required for pancreatic β-cell insulin secretion. The 2-pore-domain acid-sensitive potassium channel (TASK-1) regulates neuronal excitability and VDCC activation by hyperpolarizing the plasma membrane potential (Δψp); however, a role for pancreatic β-cell TASK-1 channels is unknown. Here we examined the influence of TASK-1 channel activity on the β-cell Δψp and insulin secretion during secretagogue stimulation. TASK-1 channels were found to be highly expressed in human and rodent islets and localized to the plasma membrane of β-cells. TASK-1-like currents of mouse and human β-cells were blocked by the potent TASK-1 channel inhibitor, A1899 (250nM). Although inhibition of TASK-1 currents did not influence the β-cell Δψp in the presence of low (2mM) glucose, A1899 significantly enhanced glucose-stimulated (14mM) Δψp depolarization of human and mouse β-cells. TASK-1 inhibition also resulted in greater secretagogue-stimulated Ca(2+) influx in both human and mouse islets. Moreover, conditional ablation of mouse β-cell TASK-1 channels reduced K2P currents, increased glucose-stimulated Δψp depolarization, and augmented secretagogue-stimulated Ca(2+) influx. The Δψp depolarization caused by TASK-1 inhibition resulted in a transient increase in glucose-stimulated mouse β-cell action potential (AP) firing frequency. However, secretagogue-stimulated β-cell AP duration eventually increased in the presence of A1899 as well as in β-cells without TASK-1, causing a decrease in AP firing frequency. Ablation or inhibition of mouse β-cell TASK-1 channels also significantly enhanced glucose-stimulated insulin secretion, which improved glucose tolerance. Conversely, TASK-1 ablation did not perturb β-cell Δψp, Ca(2+) influx, or insulin secretion under low-glucose conditions (2mM). These results reveal a glucose-dependent role for β-cell TASK-1 channels of limiting glucose-stimulated Δψp depolarization and insulin secretion, which modulates glucose homeostasis.
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Affiliation(s)
- Prasanna K Dadi
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
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Altered and dynamic ion selectivity of K+ channels in cell development and excitability. Trends Pharmacol Sci 2014; 35:461-9. [PMID: 25023607 DOI: 10.1016/j.tips.2014.06.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 06/11/2014] [Accepted: 06/12/2014] [Indexed: 12/21/2022]
Abstract
K(+) channels play a key role in regulating cellular excitability. It was thought that the strong K(+) selectivity of these channels was static, only altered by mutations in their selectivity filter, which can cause severe genetic disorders. Recent studies demonstrate that selectivity of K(+) channels can also exhibit dynamic changes. Under acidic conditions or in low extracellular K(+) concentrations, the two-pore domain K(+) channel (K2P) TWIK1 becomes permeable to Na(+), shifting from an inhibitory role to an excitatory role. This phenomenon is responsible for the paradoxical depolarization of human cardiomyocytes in pathological hypokalemia, and therefore may contribute to cardiac arrhythmias. In other cell types, TWIK1 produces depolarizing leak currents under physiological conditions. Dynamic ion selectivity also occurs in other K2P channels. Here we review evidence that dynamic selectivity of K2P channels constitutes a new regulatory mechanism of cellular excitability, whose significance is only now becoming appreciated.
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Abstract
PURPOSE/AIM Changes in pH are not infrequently encountered in clinical situations and can be associated with significant effects on ion channels, mitochondria and axon function. The purpose of this paper is to study the modulatory effects of pH on the anoxic response in peripheral nerve. MATERIALS AND METHODS A total of 48 rat sciatic nerves were studied in vitro in a perfusion apparatus. Experiments were carried out at 6 pH levels from 6.0 to 7.8. RESULTS The amplitude of the nerve action potential (NAP) drops more dramatically with repetitive periods of anoxia when the pH is reduced below 6.5. In addition, velocity decreases and duration increases more with each cycle of anoxia at low pH values. Despite these effects of pH on recovery after anoxia, there was no significant effect of pH on the time course of changes during anoxia. During recovery from anoxia, the NAP recovered more slowly when the pH was lowered. CONCLUSIONS The pattern of changes in amplitude, velocity and duration suggest that they may be due to interference of high hydrogen ion concentrations with sodium and potassium channel function.
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Acid-sensing hypothalamic neurons controlling arousal. Cell Mol Neurobiol 2014; 34:777-89. [PMID: 24798513 DOI: 10.1007/s10571-014-0065-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Accepted: 04/16/2014] [Indexed: 12/30/2022]
Abstract
Breathing and vigilance are regulated by pH and CO2 levels in the central nervous system. The hypocretin/orexin (Hcrt/Orx)- and histamine (HA)-containing hypothalamic neurons synergistically control different aspects of the waking state. Acidification inhibits firing of most neurons but these two groups in the caudal hypothalamus are excited by hypercapnia and protons, similar to the chemosensory neurons in the brain stem. Activation of hypothalamic wake-on neurons in response to hypercapnia, seen with the c-Fos assay, is supported by patch-clamp recordings in rodent brain slices: Hcrt/Orx and HA neurons are excited by acidification in the physiological range (pH from 7.4 to 7.0). Multiple molecular mechanisms mediate wake-promoting effects of protons in HA neurons in the tuberomamillary nucleus (TMN): among them are acid-sensing ion channels, Na(+),K(+)-ATPase, group I metabotropic glutamate receptors (mGluRI). HA neurons are remarkably sensitive to the mGluRI agonist DHPG (threshold concentration 0.5 µM) and mGluRI antagonists abolish proton-induced excitation of HA neurons. Hcrt/Orx neurons are excited through block of a potassium conductance and release glutamate with their peptides in TMN. The two hypothalamic nuclei and the serotonergic dorsal raphe cooperate toward CO2/acid-induced arousal. Their interactions and molecular mechanisms of H(+)/CO2-induced activation are relevant for the understanding and treatment of respiratory and metabolic disorders related to sleep-waking such as obstructive sleep apnea and sudden infant death syndrome.
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Veale EL, Hassan M, Walsh Y, Al-Moubarak E, Mathie A. Recovery of current through mutated TASK3 potassium channels underlying Birk Barel syndrome. Mol Pharmacol 2013; 85:397-407. [PMID: 24342771 DOI: 10.1124/mol.113.090530] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
TASK3 (TWIK-related acid-sensitive K(+) channel 3) potassium channels are members of the two-pore-domain potassium channel family. They are responsible for background leak potassium currents found in many cell types. TASK3 channels are genetically imprinted, and a mutation in TASK3 (G236R) is responsible for Birk Barel mental retardation dysmorphism syndrome, a maternally transmitted developmental disorder. This syndrome may arise from a neuronal migration defect during development caused by dysfunctional TASK3 channels. Through the use of whole-cell electrophysiologic recordings, we have found that, although G236R mutated TASK3 channels give rise to a functional current, this current is significantly smaller in an outward direction when compared with wild-type (WT) TASK3 channels. In contrast to WT TASK3 channels, the current is inwardly rectifying. Furthermore, the current through mutated channels is differentially sensitive to a number of regulators, such as extracellular acidification, extracellular zinc, and activation of Gαq-coupled muscarinic (M3) receptors, compared with WT TASK3 channels. The reduced outward current through mutated TASK3_G236R channels can be overcome, at least in part, by both a gain-of-function additional mutation of TASK3 channels (A237T) or by application of the nonsteroidal anti-inflammatory drug flufenamic acid (FFA; 2-{[3-(trifluoromethyl)phenyl]amino}benzoic acid). FFA produces a significantly greater enhancement of current through mutated channels than through WT TASK3 channels. We propose that pharmacologic enhancement of mutated TASK3 channel current during development may, therefore, provide a potentially useful therapeutic strategy in the treatment of Birk Barel syndrome.
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Affiliation(s)
- Emma L Veale
- Medway School of Pharmacy, University of Kent and University of Greenwich, Kent, United Kingdom
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Abstract
Much excitement surrounded the proposal that a family of endo-lysosomal channels, the two-pore channels (TPCs) were the long sought after targets of the Ca(2+) -mobilising messenger, nicotinic acid adenine dinucleotide phosphate (NAADP). However, the role of TPCs in NAADP signalling may be more complex than originally envisaged. First, NAADP may not bind directly to TPCs but via an accessory protein. Second, two papers recently challenged the notion that TPCs are NAADP-regulated Ca(2+) channels by suggesting that they are highly selective Na(+) channels regulated by the lipid phosphatidylinositol 3,5-bisphosphate and by ATP. This paper aims critically to evaluate the evidence for TPCs as NAADP targets and to discuss how the new findings fit in with what we know about endo-lysosomal Ca(2+) stores.
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